struct page *d_page;
         /* Starting object index within @s_page which used for live object
          * in the subpage. */
-       int index;
+       int obj_idx;
 };
 
 static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
        unsigned long handle;
        struct page *s_page = cc->s_page;
        struct page *d_page = cc->d_page;
-       unsigned long index = cc->index;
+       int obj_idx = cc->obj_idx;
        int ret = 0;
 
        while (1) {
-               handle = find_alloced_obj(class, s_page, index);
+               handle = find_alloced_obj(class, s_page, obj_idx);
                if (!handle) {
                        s_page = get_next_page(s_page);
                        if (!s_page)
                                break;
-                       index = 0;
+                       obj_idx = 0;
                        continue;
                }
 
                used_obj = handle_to_obj(handle);
                free_obj = obj_malloc(class, get_zspage(d_page), handle);
                zs_object_copy(class, free_obj, used_obj);
-               index++;
+               obj_idx++;
                /*
                 * record_obj updates handle's value to free_obj and it will
                 * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
 
        /* Remember last position in this iteration */
        cc->s_page = s_page;
-       cc->index = index;
+       cc->obj_idx = obj_idx;
 
        return ret;
 }
                if (!zs_can_compact(class))
                        break;
 
-               cc.index = 0;
+               cc.obj_idx = 0;
                cc.s_page = get_first_page(src_zspage);
 
                while ((dst_zspage = isolate_zspage(class, false))) {